The present invention relates to a process and apparatus for producing splined driving belts, the process being of the type comprising the steps of:
making a flexible annular element of an elastomeric vulcanized material having a flattened rectangular section and incorporating at least a textile reinforcing layer extending parallelly to the major sides of said section to a predetermined distance from an operating surface defined by at least one of said major sides of the extension of the flexible annular element; PA1 mounting the flexible annular element to at least a support roller; PA1 moving the flexible annular element with a uniform movement in the direction of its longitudinal extension by driving in rotation said at least one support roller; PA1 removing the elastomeric material from the flexible annular element for producing a number of longitudinal grooves on said operating surface. PA1 at least a support roller designed to operatively engage a flexible annular element of vulcanized rubber having a flattened rectangular section and incorporating at least a textile reinforcing layer extending parallelly to the major sides of said rectangular section to a predetermined distance from an operating surface defined by at least one of said major sides on the extension of the flexible annular element; PA1 actuator means designed to drive in rotation said at least one support roller so as to move the flexible annular element in the direction of its longitudinal extension; PA1 cutting means designed to act on the operating surface of the annular element in order to produce a number of parallel grooves extending over the whole longitudinal extension of the annular element itself. PA1 carrying out one series of longitudinal notches on said operating surface, which notches are spaced apart from each other by the same distance and extend parallelly in the section of the annular element according to an inclined direction relative to the normal of the operating surface; and PA1 according to a depth lower than the distance between the textile reinforcing layer and the operating surface itself; PA1 carrying out a second series of longitudinal notches on said operating surface, which notches are spaced apart from each other by the same distance, extend parallelly in the section of the annular element and are united each with one of the notches of the first series so as to form said longitudinal grooves in the flexibile annular element. PA1 one set of knives disposed parallelly in side by side relation and simultaneously movable from a rest position in which they are spaced apart from the annular element to a cutting position in which they penetrate into the operating surface of the annular element by a predetermined amount and according to an inclined direction relative to the normal of the operating surface itself; PA1 a second set of knives disposed parallelly in side by side relation and simultaneously movable from a rest position in which they are spaced apart from the annular element to a cutting position in which they penetrate into the operating surface of the annular element by a predetermined amount and according to an inclined direction relative to the cutting direction of the first set of knives.
The above process is is accomplished by an apparatus of the type comprising:
The process can be applied in order to make at least a split on the belt or to form a single belt with several splits or several belts disposed in side-by-side relation with the respective splits.
It is known that splined driving belts essentially consist of an annular element made of vulcanized rubber of substantially flattened rectangular section and incorporating a textile reinforcing layer extending parallelly to the major sides of said section.
Formed on one operating surface of the annular element defined by the extension of one of the major sides of its section, is a plurality of longitudinal parallel grooves which are generally in the form of "V" and are spaced apart from each other by the same distance.
The presence of these grooves gives rise to corresponding ribs which are in the form of "V" too.
The ribs are designed to be accommodated into respective grooves formed in the pulleys to which the belt will be mounted for use.
Presently there are different methods for producing belts of the above described type.
One of these methods is described in U.S. Pat. No. 3,893,116 according to which provision is made for winding in succession one layer made of raw elastomeric material, a textile reinforcing layer and a second layer made of raw elastomeric material on a cylindrical matrix of vulcanized rubber, provided with parallel ribs on the outer surface thereof.
Subsequently a vulcanization step is carried out during which the semifinished product is pressed against the matrix.
Under this situation the ribs exhibited by the matrix penetrate into the first elastomeric layer thereby giving rise to a plurality of circumferential grooves on the inner surface of the vulcanized product.
The vulcanized product is then disengaged from the matrix and, if necessary, split into several parts on the circumferential extension thereof so as to give rise to a number of driving belts of the desired width.
However the methods of the above described type have some drawbacks resulting from the fact that it is rather difficult to control the burying of the raw elastomeric material into the matrix ribs. It is therefore difficult to achieve a very precise and accurate working on the finished belts.
In greater detail it is to be pointed out that above all when belts of small-sized section are manufactured, it is difficult to obtain precise size features for the grooves as well as an exact positioning of the textile reinforcing element in the belt section.
In this connection it is to be pointed out that the groove configuration is of the greatest importance for achieving a correct behaviour of the belt when in use on the respective pulleys.
At the same time, the positioning of the textile reinforcing element is also of the greatest importance for the correct distribution of the efforts that the belt must undergo under use conditions.
In addition a further drawback of the described methods resides in that the availability of a great number of matrices is necessary in order to make belts having the required different configurations and size characteristics in compliance with the market needs.
Another fact to be taken into due account is that the production processes of the above type are rather complicated and consequently bring about an increase in the manufacturing cost.
According to another method described in U.S. Pat. No. 4,332,576 used for the production of splined belts, the manufacture of the flexible annular element designed to constitute the finished belt is first carried out, said element consisting of two or more layers of elastomeric material incorporating at least a layer of textile reinforcing material therebetween.
When the elastomeric material is still in a raw state, the flexible annular element is engaged between two mutually spaced apart pulleys between which two moulding units are arranged each designed to operate on one of the rectilinear layers exhibited by the extension of the annular element stretched between the two pulleys.
Each moulding unit substantially comprises two heated plates which can be moved close to each other in order to compress the length of the annular element interposed therebetween.
At least one of said plates, that is the one facing the inner surface of the extension of the annular element is such shaped as to produce the desired grooves on the belt which is being manufactured.
Consequently, the annular element length which is enclosed between the heated plates undergoes a moulding action simultaneously with a vulcanization action.
At the end of a predetermined lapse of time, sufficient for the elastomeric material to be vulcanized, plates are moved away from each other and, by driving the pulleys in rotation, the annular element is moved forward so that a new length of the extension thereof is located between the plates, being ready for moulding and vulcanization.
The manufacture of the belt is over when the annular element has been moulded and vulcanized over the whole extension thereof.
This production process too has the drawback that it does not allow an easy control of the penetration of the elements designed to mould the elastomeric material into the material itself.
It is consequently difficult to obtain a precise working above all when small-sized belts have to be produced.
In addition, as moulding and vulcanization are carried out repeatedly on the different lengths of the flexible annular element extension, it is rather problematic to obtain a perfectly homogeneous vulcanization degree over the whole elastomeric material forming the belt.
It is also to be pointed out that the method involves long working times and the availability of heated plates of different structural configuration for achieving the different types of belt required on the market.
Working processes are known as well in which the grooves on the operating surface of the annular element are carried out by mechanical working on the previously vulcanized elastomeric material.
In greater detail, the vulcanized annular element having a flattened annular configuration is provided to be fitted on a support roller in a reversed condition, that it in such a manner that its operating surface is located on the outer side of its circumferential extension.
Then the support roller is put in rotation and afterwards the annular element is submitted to the action of an abrasive grinding wheel the profile of which matches the shape of the profile of the grooves to be produced on the belt being worked.
This method allows more precise workings to be carried out as compared with the previously described methods, as the manufacture of grooves on previously vulcanized elastomeric material eliminates all problems connected with the difficulty of checking the deformations of the raw elastomeric material during the moulding step.
However it has been found that in this case too the accuracy of working is not completely satisfactory, above all when the groove sizes are very small. In fact the accuracy in working is tightly connected with the granulometry of the grinding wheel used, the value of which cannot be lower than certain limits.
In particular the radius of the groove bottom cannot be reduced to minimum values which would be desirable for the good operation of the belts on the pulleys.
In addition this method too has the problem that a great number of different grinding wheels are necessary for the manufacture of belts having different structure and size features.
Moreover, the abrasive action of the grinding wheels gives rise to a surface overheating which is sometimes harmful to the physical characteristics of the surface generated by the grinding operation.
Finally it is to be pointed out that the above operation is rather slow, which results in a higher cost for the product, and also involves the disadvantage of an increased noise.